1. Field of the Invention
This invention relates, generally, to the fields of biophysics, tissue regeneration, tissue culture and neurobiology. More particularly, it relates to a method and apparatus for potentiation of or controlling the growth of biological cells and tissue in vitro.
2. Description of the Prior Art
Conventional cell culturing involves placing a small number of cells into a nutrient-rich media, typically a petri dish or flask, and allowing the cells to grow and multiply. The result is a two dimensional growth of cells. This provides limited insight as to how the cells would actually grow and multiply in three dimensions, i.e., in vivo. Without a proper three-dimensional assembly, epithelial and mesenchymal cells, which are the basic cells that differentiate tissue into specific organ functions, lack the proper indicators for growing into a variety of cells that make up a specific tissue. It is known that cells self-associate in the body, i.e., replication involves association with the proper connections in the surrounding environment, as in the body, for proper growth clues to naturally form. It is therefore desirable to have a culture environment that simulates tissue assembly in the body to provide the proper growth clues to the cells.
Systems are known that attempt to provide a three-dimensional cell culture environment. The bioreactor developed by NASA in the 1980s is one such system. The bioreactor is a can-like rotating vessel with a membrane for gas exchange that allows nutrients in and carbon dioxide and wastes out. As the bioreactor turns, the cells continually fall through the medium yet never hit bottom, thus promoting self-association in a proper growth environment. As such, the cells form clusters and grow and differentiate as they would in the body. This culture environment is referred to as simulated or modeled microgravity.
The desire to provide three-dimensional cell cultures has led others to the use of time varying electromagnetic fields and other mechanical devices to help grow and orient three-dimensional tissue in vitro.
WO 02/051985 teaches a method of culturing cells in a bioreactor that supplies a continuous supply of culture medium. Magnetic material in the form of micro or nano particles is attached to the tissue forming cells. The cells are then subjected to a magnetic field that varies sinusoidally at a frequency between 0.1-10.0 Hz. The resulting mechanical stresses are applied to the cells and the result of such mechanical stress is tissue growth. More particularly, the invention provides a method for culture while subjecting tissue or cells to repeatedly applied magnetically-generated mechanical stresses and the result of such mechanical stress is tissue or cell growth. The stresses may be administered via a magnetic material attached to the cells such as micro or nano particles, or may be a magnetic material that is inserted into the culture medium as a ferrofluid.
Simon et al. in the Journal of Applied Physics (2000) and in the American Journal of Physics (June 2001) disclose levitation of living things such as frogs using permanent magnets and diamagnetic plates. No cell culture is positioned in the magnetic field between the permanent magnets and the diamagnetic plates. None of the cells that collectively form the frog are changed when the frog is released from the magnetic field.
U.S. Pat. No. 5,396,136 to Pelrine discloses a two dimensional array of permanent magnets levitated over a layer of pyrolytic graphite, a diamagnetic material. No cell culture is positioned in the magnetic field between the permanent magnets and the diamagnetic plate. The levitation of permanent inanimate magnets has potential utility in connection with magnetic levitation trains or in instruments such as accelerometers or gyroscopes.
U.S. Pat. No. 6,203,487 to Consigny discloses microspheres that are incorporated into cells. The microspheres have a diameter of about four and one-half microns (4.5 μm) and are guided by magnets to a target tissue such as blood vessels damaged during a surgical procedure. Three dimensional cell growth is not disclosed by Consigny nor would such cell growth be likely in view of the very small size of the microspheres. In balloon angioplasty where artery-clogging plaque is removed, it is desirable to deliver single cells to the damaged artery by following the Consigny teachings but it would be undesirable to deliver an artery-clogging three dimensional mass of cells to such a location. Therefore it may be concluded that the Consigny teachings do not include the formation of three dimensional cell growth.
It is desirable to provide a realistic environment and in vivo-like growth conditions to develop in vitro models of cell and tissue biology and functionality that replicate the conditions in the body in which the cells and tissue normally grow. However, the systems and methods currently known in the art do not provide this desirable realistic environment. The simulation of microgravity associated with the continuous rotation of a culture chamber creates a problem associated with the alteration of genes and thus protein expression due to the constant randomization of the gravity vector attributed to the continuous rotation.
It would also be desirable to provide a system that does not require electrically conductive channels, thereby eliminating the need for a constant supply of electricity.
There remains a need, therefore, for a system and method to provide a realistic environment for developing in vitro models of cell and tissue biology and functionality that replicate the conditions in the body in which the cells and tissue normally grow.
However, in view of the prior art considered as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in the pertinent art how the identified need could be fulfilled.